Republicans now have approximately a one-in-four chance of winning enough Senate seats in the Nov. 2 elections to claim an outright majority of the chamber, FiveThirtyEight’s latest forecasting model shows.

That the disposition of the Senate is in doubt is not a new development; the model had assigned Republicans better than a one-in-five chance of claiming the chamber upon its debut at the New York Times two weeks ago. Nevertheless, nearly every day now seems to bring another sour piece of polling news for the Democrats.

Today, for instance, a poll for the Washington Post showed Republicans with a 13-point lead among likely voters on the generic Congressional ballot, which would imply a potentially catastrophic outcome for Democrats. Although the polling trend is not always uniform or predictable — Gallup’s generic ballot poll, which had given Republicans a 10-point advantage last week, now shows the two parties running evenly — the Democrats’ hopes for a spontaneous political recovery this summer now appear to be dashed.